JP5559732B2 - Battery manufacturing method and welding method - Google Patents

Description

  The present invention relates to a battery manufacturing method and a welding method, and more particularly to a current collector plate welding technique for electrically connecting adjacent unit cells.

  Some secondary batteries such as nickel metal hydride batteries mounted on a vehicle are configured to be connected to each other using a short side surface of a rectangular parallelepiped battery case as a partition wall. Each battery case includes an electrode plate group formed by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween, and a current collector plate and an electrolyte solution bonded to both sides thereof. A through hole is formed in the partition wall between the adjacent battery cases, and the connection protrusions of the current collector plate are fitted into the through holes, and the adjacent unit cells are electrically connected by welding the connection protrusions.

  As the welding, for example, resistance welding is used, and welding is performed by pressing the welding electrode in a state where both ends of the current collector plate are in contact with each other while supporting both ends, and passing a predetermined welding current through the welding electrode. .

  Resistance welding (projection resistance welding or the like) is known. For example, in Patent Document 1 below, a detection unit that detects a welding process for each hit point and a first memory that counts a signal from the detection unit as the number of hit points. Part, a second storage unit storing pre-welding conditions according to a predetermined number of hit points, and a pre-welding condition of the second storage unit according to the number of hit points output from the first storage unit A resistance welding pre-energization control device including a condition changing unit and a control unit that controls welding under pre-welding conditions output from the condition changing unit is disclosed.

  Further, Patent Document 2 below is a resistance welding method in which metal base materials provided with metal coating layers on their surfaces are welded with protrusions formed on the metal base material, and the metal coating layers are A period from the middle to the end of energization when welding at the same time with a plurality of protrusions formed on the metal base material having a lower electrical resistance value than the metal base material and a lower melting point than the metal base material It is disclosed to reduce the welding current.

JP-A-8-238574 JP 2004-90037 A

  By the way, when electrically connecting adjacent unit cells, a through hole is formed in the partition wall, and a connecting protrusion of the current collector plate is inserted into the through hole and welded, so that the through hole is sealed. In addition, a sealing material such as an O-ring is required, and when the current collector plate is welded, it is necessary to surely perform welding and to securely seal the through hole by tightening the sealing material.

  When heat is applied to the current collector plate before welding and annealing is performed, the connection protrusions of the current collector plate are thermally deformed, so that it is possible to effectively tighten the sealing material during welding. Since it is necessary to anneal separately, the process becomes complicated. Therefore, there is a demand for a method that can reliably weld the current collector plate without thermal annealing and can tighten the sealing material.

  The object of the present invention is to weld the members to be welded (battery current collector plates) to each other without annealing by applying heat or when the annealing is insufficient, and at the same time sufficiently tighten the sealing material. It is to provide a method that can.

The present invention, partition walls through holes are formed between the current collector plate for positive and negative sides of the cell are disposed adjacent to each other, and the sealing material is disposed between the said collector barrier rib, a method of manufacturing a battery of welding connection protrusion between the current collector plate with the through hole, a lower amount of heat per unit time than welding current, current value at 2.0KA～4.0KA, A first energization step of energizing the connection protrusions with an energization time of 20 msec to 100 msec; and a second energization step of energizing a welding current and welding the connection protrusions after the first energization. It is characterized by. In one embodiment of the present invention, before Symbol second energizing step includes the steps of energizing the welding current of a constant current for a predetermined time, and a step of reducing the energization current sequentially.

  According to the present invention, the first energization performed prior to the second energization for welding causes thermal deformation substantially similar to thermal annealing to the connection protrusions of the current collector plate, so that Even if the annealing treatment by application is not performed or the annealing treatment is insufficient, the connection protrusions of the current collector plates can be welded together to secure the tightening amount of the sealing material.

It is a block diagram of the secondary battery in embodiment. It is the A section enlarged view in FIG. It is a graph which shows the electricity supply profile of embodiment. It is a graph which shows the electricity supply profile of a prior art. It is a graph which shows the amount of tightening when a 1st electricity supply is changed. It is a block diagram of other embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking a secondary battery mounted on a vehicle as an example. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments.

  In FIG. 1, the structure of the secondary battery in this embodiment is shown. The secondary battery 10 is formed by connecting a rectangular parallelepiped battery case 12 having a narrow short side surface and a wide long side surface, sharing the short side surface as a partition wall 16. In the figure, six battery cases 12 are shown, but the number is arbitrary. The upper surface opening of each battery case 12 is integrally closed with an integral lid 13.

  In each battery case 12, a power generation element including an electrode plate group 14 formed by laminating a positive electrode plate and a negative electrode plate via a separator and current collector plates 20a and 20b bonded to both sides thereof is accommodated together with an electrolyte. A single cell. The positive electrode plate and the negative electrode plate of the electrode plate group 14 protrude on opposite sides and are joined to the current collector plates 20a and 20b, respectively.

  A through hole for connection is formed in the upper part of the partition wall 16 between the adjacent battery cases 12 and 12. In addition, connection protrusions that fit into the through holes of the partition wall 16 are formed on the upper portions of the current collector plates 20a and 20b, respectively, and the connection protrusion of the current collector plate 20a and the current collector plate 20b are disposed between the adjacent battery cases 12 and 12. The connection projections are welded by resistance welding (preferably projection welding). The resistance welding method will be further described later.

  Through holes are also formed on the outer short sides of the battery case 12 at both ends, and a positive electrode terminal 22 and a negative electrode terminal 24 are mounted, respectively. A current collector plate 20 a of the battery case 12 adjacent to the positive electrode terminal 22 is connected to the positive electrode terminal 22. A current collector plate 20 b of the battery case 12 adjacent to the negative electrode terminal 24 is connected to the negative electrode terminal 24.

  As described above, the plurality of single cells are connected in series, and a predetermined DC voltage is output between the positive terminal 22 and the negative terminal 24 at both ends.

  FIG. 2 shows a welded portion of the current collector plates 20a and 20b in the portion A in FIG.

  A through hole 30 is formed in a part of the partition wall 16, and the connection protrusion 21 a of the current collector plate 20 a and the connection protrusion 21 b of the current collector plate 20 b are both fitted into and contact with the through hole 30. An O-ring 32 as a sealing material is attached between the through hole 30 and the connection protrusions 21a and 21b. In a state where the O-ring 32 is mounted, a pair of welding electrodes are arranged so as to sandwich the connection projections 21a and 21b of the current collector plates 20a and 20b, and the connection projections 21a and 21b are pressed from both sides to obtain a predetermined load. The connection projections 21a and 21b are resistance-welded by flowing a welding current in a state in which is applied.

  In such a configuration, conventionally, the current collector plates 20a and 20b are both subjected to resistance welding after being subjected to an annealing treatment by applying heat, and the connection protrusions 21a and 21b of the current collector plates 20a and 20b are heated by annealing. Since it deforms, it is possible to effectively tighten the O-ring 32 as a sealing material at the time of resistance welding, but the treatment becomes complicated because it needs to be separately annealed with a heater before welding.

  Therefore, in the present embodiment, resistance welding is performed in a state where the current collector plates 20a and 20b are not annealed by applying heat. Specifically, before supplying the welding current to the connection projections 21a and 21b of the current collector plates 20a and 20b, first energization is performed prior to this, and the connection projections 21a and 21b are heated by the first energization. Thermal deformation substantially similar to the annealing treatment by applying heat is generated. Since the purpose of the first energization is not the welding of the connection protrusions 21a and 21b, the current value is made smaller than a predetermined welding current necessary for welding the connection protrusions 21a and 21b, and the amount of heat per unit time. Is smaller than the second energization.

That is, in this embodiment, the connection protrusions 21a and 21b of the current collector plates 20 and 20b are welded by the following two processes.
(1) Energize a current value smaller than the welding current (first energization).
(2) Thereafter, welding is performed by applying a welding current (second energization).

  FIG. 3 shows an energization profile in the present embodiment. In the figure, the horizontal axis represents time, and the vertical axis represents the energization current value.

  First, the first energization 100 is started at a certain time t1. In the first energization 100, a constant current smaller than the welding current is passed through the connection protrusions 21a and 21b. Then, at the time t2, the first energization is terminated, and then the second energization 102 is started. In the second energization 102, a welding current necessary for welding the connection protrusions 21a and 21b is passed. The second energization 102 has a constant value from time t2 to time t3, and then decreases sequentially from time t3 to time t4 and becomes zero at time t4.

  FIG. 4 shows a conventional energization profile for comparison with the energization profile of the present embodiment. Conventionally, the current collector plates 20a and 20b are preliminarily annealed by applying heat, and a welding current is supplied from time t1 to time t5, and then a current lower than the welding current is applied from time t5 to time t6. Shed.

  Comparing FIG. 3 and FIG. 4, in this embodiment, there are two points: the first energization 100 exists before welding, and the profile that sequentially decreases at the time t3 to t4 of the second energization 102 exists. In FIG. The first energization 100 can resistance-heat the connection protrusions 21a and 21b to obtain the same thermal deformation effect as the annealing process by applying heat, and the tightening amount of the O-ring 32 can be adjusted to an appropriate amount. Therefore, the annealing process by applying heat is not required (annealingless). Further, the decrease of the second energization 102 at the times t3 to t4 can secure the amount of heat necessary for welding and suppress damage to the partition wall 16 or the O-ring 32 to the minimum.

  FIG. 5 shows a change in the tightening amount of the O-ring 32 when the energization amount of the first energization 100 is changed. This is a case where the first energization 100 is flowed at times t1 to t2 and the second energization 102 is flowed at times t2 to t4, and the energization amount of the first energization 100 is changed with the second energization 102 being constant.

  In the figure, a solid line 100b is a reference energization amount, an energization amount relatively smaller than this is indicated by a one-dot chain line 100a, and an energization amount relatively larger than the reference energization amount is indicated by a two-dot chain line 100c.

  Also, the tightening amounts (or upsetting amounts) of the O-ring 32 when the energization amounts 100a, 100b, and 100c are supplied are indicated by 200a, 200b, and 200c in the drawing, respectively. The tightening amounts corresponding to the energization amounts 100a, 100b, and 100c are the tightening amounts 200a, 200b, and 200c, respectively. If the tightening amount of the O-ring 32 is 0.5 mm or more, for example, it can be regarded as a sufficient level.

  When the energization amount of the first energization 100 increases, the tightening amount of the O-ring 32 increases accordingly. The tightening amount 200b at the reference energization amount 100b is about 0.6 mm, and a sufficient level is secured.

  The tightening amount 200c when the energization amount 200c is relatively large is sufficient as 0.7 mm, but burning of a part of the partition wall 16 occurs.

  The tightening amount 200a when the energization amount 200a is relatively small is less than 0.5 mm, and the O-ring 32 is not sufficiently tightened.

It is desirable that the first energization 100 is of a level that can sufficiently secure the tightening amount of the O-ring 32 and that does not cause burning of the partition wall 16 and melting (welding) of the connection protrusions 21a and 21b. Examples of ranges are as follows.
Current value: 2.0 KA to 4.0 KA
Energization time: 20msec~100 m sec
If the current value is less than 2.0 KA or if the energization time is shorter than 20 msec, the tightening amount of the O-ring 32 cannot be secured sufficiently, and if the current value is greater than 4.0 KA or if the energization time is longer than 100 msec. This is because the O-ring 32 and the partition wall 16 are damaged, which is not preferable.

  Incidentally, the applicant of the present application does not change the resistance values of the connection protrusions 21a and 21b when the energization amount 200a is relatively small, and gently reduces the resistance values of the connection protrusions 21a and 21b when the reference energization amount 200b. It is confirmed that the resistance values of the connection protrusions 21a and 21b are steeper than when the welding current 102 is passed when the energization amount 200c is relatively large. Considering that the connection protrusions 21a and 21b are both conductors, and the resistance value of the conductor increases with temperature, in the case of the relatively small energization amount 200a, almost no heat is generated, and in the case of the reference energization amount 200b. In the case of a relatively large energization amount 200c, it can be said that heat generation similar to that during welding occurs. At the reference energization amount 200b, the resistance value rises gently and shows an increase of about 50 to 100 μΩ from the rise start to the second energization start.

  Then, when the second energization 102 is started, a sudden rise is shown, and here, heat is generated for the first time.

  In addition, when this application applicant welds the connection protrusions 21a and 21b only by the 2nd electricity supply 102, without performing the 1st electricity supply 100, the tightening amount of O-ring 32 is less than 0.5 mm and it is insufficient. I have confirmed.

  The appropriate range of the first energization 100 is determined by the energization current and the energization time. However, if the current value is set to a certain value or more, welding is performed, and if the current value is too low, the energization time is increased more than necessary. Since this is inefficient, it is desirable to determine the balance between the energization current and the energization time while monitoring the amount of increase in resistance value.

In addition, the energization current and energization time of the second energization 102 may be adjusted up or down within a certain range. Examples of the range are as follows.
Current value: 5KA to 10KA, preferably 7KA to 8KA
Energizing time: 10 msec to 30 msec, preferably 15 msec to 25 msec
The ratio of the welding current 102 to the entire reduction profile can be, for example, 30% to 50% of the time t3 to t5.

  In the present embodiment, the connection protrusions 21 a and 21 b of the current collector plates 20 a and 20 b are welded together by a combination of the first energization 100 and the second energization 102, and the second energization 102 is performed by executing the first energization 100. This has the effect of shortening the effective time of the welding current, that is, the energization time of the welding current.

  Furthermore, since the connection protrusions 21a and 21b are thermally deformed to some extent by the first energization 100, the allowable variation range of the welding current in the second energization 102 is expanded more than before, which is also effective from the viewpoint of ensuring robustness. . That is, since the first energization 100 is present, the lower limit value of the welding current can be shifted downward as compared with the prior art, and burning of the partition wall 16 due to excessive heat is prevented by the decreasing slope (down slope) at time t3 to t4. Therefore, the upper limit value of the welding current can also be shifted upward as compared with the prior art. Ensuring such robustness is particularly significant when the secondary battery 10 is mass-produced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation is possible.

  For example, in the present embodiment, the first energization 100 and the second energization 102 are continuously performed, but an interval may be set between the first energization 100 and the second energization 102 for a predetermined time. . However, by continuously performing the first energization 100 and the second energization 102, there is an advantage that the throughput is improved and the thermal deformation caused by the first energization 100 can be more reliably used by the second energization 102. .

  In the above embodiment, the connection protrusions are provided on both the positive and negative current collector plates and are fitted in the through holes. However, the connection protrusions are provided only on the positive and negative current collector plates. The connecting portion of the other current collector plate may be a flat shape or a non-projecting shape such as a concave portion.

  Further, in the above embodiment, the current collector plate that has not been annealed is used, but it is also effective when annealing is insufficient and the sealing material cannot be sufficiently tightened.

  Moreover, in the said embodiment, although the welding of the current collector plate was demonstrated, this invention can be utilized even if it welds in the state which arranged the sealing material between two to-be-welded members also in another to-be-welded member. It is. For example, as shown in FIG. 6, the present invention can also be used for manufacturing a battery 40 (in the figure, a battery pack in which ten batteries 40 are connected in series). Specifically, the + terminal 60 and the − terminal 62 protruding from the lid of the battery 40 are welded by placing a sealing material between the lid and other members so that the electrolyte does not leak out of the case. However, the welding in that case may be performed by the first energization and the second energization. 6A is a plan view, FIG. 6B is a front view, and FIG. 6C is a right side view. Reference numeral 64 is a connection conductor, and reference numeral 66 is a band for integrally fixing the cells. Indicates.

  10 secondary battery, 12 battery case, 14 electrode plate group, 16 partition, 20a, 20b current collector plate, 21a, 21b connection protrusion, 30 through hole, 32 O-ring.

Claims (2)

Single cell the positive electrode side and the partition wall having a through hole is formed between the negative electrode current collector plate is disposed adjacent to each other, and the sealing material is disposed between the said collector barrier rib, the through-hole A method of manufacturing a battery for welding the connection protrusions of the current collector plates using ,
Amount of heat per unit time is lower than the welding current, current value at 2.0KA～4.0KA, a first power supply step of energizing time to energize the current of 20msec~100msec to the connection projection,
A second energization step of energizing a welding current and welding the connection protrusions after the first energization;
A method for producing a battery, comprising: In the manufacturing method of the battery of Claim 1,
The second energization step includes
Energizing the welding current at a constant current for a predetermined time;
A step of sequentially reducing the energization current;
A method for producing a battery , comprising:

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